解决KLOXO域名解析漏洞的修补

Linode发来的关于服务器域名解析漏洞的警告：

Hello, It has come to our attention that your Linode is running an open resolver. This is a concern for us because this configuration means your Linode could easily be used in a DNS amplification attack.

We kindly ask that you investigate this matter and take appropriate action. If you are running a resolver as part of your networking configuration, you'll likely want to adjust it so that only internal requests are accepted. Please update us as soon as possible! If you have any questions or concerns, please let us know. ...